Frequently Asked Questions

A CNC machining center
or milling machine that has 3-axis helical interpolation capability.

Will I need sophisticated equipment to
program a thread milling operation (such as an NPT thread)?

No. In fact Widia GTD provides this service
free of charge for any customer who buys their product. Most
customers have learned to write their own programs from the
information Widia GTD has previously sent them. It only takes
a few minutes.

Is thread milling just
a new fad?

No. Thread milling
has been performed in real production since the mid 60's.
The advent of NC or tape-controlled machines made the process
possible, but it was a long and arduous task to create a program.
Today's CNC controls make the task very simple and extremely
accurate.

I have canned cycles for thread milling
in my CNC control now, and we have not been able to make any
thread mill work very well. Why would your mills work when others
haven't?

Widia GTD has discovered there are many
important steps to consider when preparing a program. Most canned
cycles do not take these proven steps into consideration. How
you program the tool path is critical to performance. How the
tool is made is also key. We freely offer the information we've
learned and will help you with difficult applications.

Why is everyone just
now talking about thread milling when CNC equipment has been
around for such a long time?

The reason is simple. Just
10 years ago, most machining centers being sold offered spindle
speeds with only 3,000 to 5,000 RPM as standard. These speeds
were just too slow to reach economical cutting speeds necessary
for small thread milling applications when compared to conventional
tapping. Today, CNC mills are delivered with spindle speeds
of 10,000 RPM as standard, with options up to 25,000 RPM becoming
more common. At these speeds, thread miling is more economical
than tapping and can even reduce cycle times, in most cases.

Will I have to stock my tool crib with
thread mills for every size hole and pitch as I do with taps?

No. If you buy a thread mill to produce a
1/4-24 hole, that same mill will produce any 24 pitch hole size
that is larger than 1/4-24. In fact, many of our customers have
used our thread mills to complete one-day rush jobs that would
have otherwise required several days for a special order tap.

Do I have to order
special diameter thread mills to produce different class fits
of the same major thread diameter?

No. Class fit is determined
by simply changing the machine tool offset to mill the hole
larger or smaller. Some materials have a tendency to "spring"
back after tapping or cut smaller holes. These jobs require
special H-limit taps to satisfy fit. Thread mills can produce
virtually any fit in increments of .0001" or finer if your
machine has higher resolution or repeatability.

What percentage of thread height can
I thread mill?

All Widia GTD HP thread mill products are
designed with 100% thread form as specified for that given thread
type. You will need to change your existing tap drill size to
a smaller drill in order to take advantage of this feature.
It makes no difference if you continue with the existing tap
drill you now use; however, the deburring feature of full-form
thread mills will not be used if you do.

In blind holes having
a counterbore shoulder, how close to the shoulder can I expect
to produce threads?

You can produce full threads
thread milling to within 1/4 to 1 pitch of the shoulder.

For larger thread diameters such as 1
1/4-8UN, will I still need to use secondary tapping equipment,
such as a drill press?

Thread mills require very little horsepower
to produce the desired hole, no matter how coarse the thread.
The largest thread diameter you can mill is limited to the shortest
X- or Y-limits of the machine bed. In fact, thread milling offers
the greatest cost savings by eliminating the need to set up
on another machine to complete a job.

If I break
a thread mill, will I have to rework the part with tap extractors
or EDM operations?

If you
break a thread mill in operation, the broken portion of the
thread mill will merely fall down the hole. This is because
the head of the thread mill is always smaller than the minor
thread diameter of the thread. To complete the job, simply
remove the broken piece from the hold with tweezers or needle-nose
pliers, replace the broken shank in the tool holder and touch
off the end of the tool, then rerun the thread mill cycle.
The Widia GTD thread mill will repeat to within .0005"
from mill to mill.

What industries are best suited for thread
milling?

In the beginning, we focused on valve industries,
automotive, and aerospace products that involve more difficult-to-machine
materials. We have since found that thread milling has applications
in virtually all metal working classifications. Some of our
best customers are job shops and small specialty companies that
have limited tool stocks to work from. Because of the flexibility
of a single thread mill to produce a wide range of holes, it
suites their type of work very well.

Is additional training and support available
for thread milling products?

Yes. We have technical service personnel
available to work with you. Depending on your needs, we can
arrange special presentations and training seminars.